Physics 2 test

I wish to use a positively charged rod to charge a ball by induction. Which statement is correct?

It must be a conductor

Two point charges are separated by 10.0 cm and have charges of +2.00 µC and -2.00 µC, respectively. What is the electric field at a point midway between the two charges? (ke = 8.99 ´ 109 N·m2/C2)

zero

A thin uncharged conducting spherical shell has a charge q carefully placed at its center through a small hole in the shell. The charge q does not touch the shell. What is the charge on the shell?

0

About how many electrons are in 30 grams of water (H2O)?

10^25

Electric field is dimensionally equivalent to which of the following?

n/c

A charge Q accumulates on the hollow metallic dome, of radius R, of a Van de Graaff generator. A probe measures the electric field strength at various points outside the sphere surface. If the probe is initially at a distance 3R from the sphere's center and then is moved to 4R, by what factor will the electric field reading change?

(3/4)2

If a charge +Q is placed inside a hollow isolated conductor that is originally neutral and the charge does not touch that conductor at any time:

the outside surface of the conductor will become positively charged.

At what point is the charge per unit area greatest on the surface of an irregularly shaped conducting solid?

where curvature is greatest

A charge of +2 C is at the origin. When charge Q is placed at 2 m along the positive x axis, the electric field at 2 m along the negative x axis becomes zero. What is the value of Q?

-8 C

Two equal charges, each Q, are separated by some distance. What third charge would need to be placed half way between the two charges so that the net force on each charge would be zero?

-Q/4

Electrons in a particle beam each have a kinetic energy of 3.2 ´ 10-17 J. What is the magnitude of the electric field that will stop these electrons in a distance of 0.1 m? (e = 1.6 ´ 10-19 C)

2 000 N/C

An electron is sent at high speed toward a gold nucleus (charge +79e). What is the electrical force acting on the electron when it is 3.0 ´ 10-14 m away from the gold nucleus? (e = 1.6 ´ 10-19 C, ke = 8.99 ´ 109 N·m2/C2)

20 N

Two identical iron spheres have equal positive charges and the force between them when they are 1 m apart is 1 N. What percentage of the electrons has been removed from each sphere if each sphere has 1 mole (6 ´ 1023) of iron atoms? (ke = 8.99 ´ 109 N×m2/C2, the atomic number of iron is 26, and the electron charge is -1.6 ´ 10-19 C)

4 ´ 10-10 %

Two electrons are separated by one cm. What is the ratio of the electric force to the gravitational force between them? (me = 9.11 ´ 10-31 kg, ke = 8.99 ´ 109 N×m2/C2, G = 6.67 ´ 10-11 N×m2/kg2, and e = 1.6 ´ 10-19 C)

4.2x10^42

Two point charges, separated by 1.5 cm, have charge values of +2.0 and -4.0 µC, respectively. What is the value of the mutual force between them? (ke = 8.99 ´ 109 N×m2/C2)

8.0 ´ 10-12 N

We have an initially uncharged hollow metallic sphere with radius of 5.0 cm. I place a small object with a charge of +10 µC at the center of the sphere through a hole in the surface. Find the electric field present at a point 10 cm from the sphere's center. (ke = 8.99 ´ 109 N×m2/C2)

9.0 ´ 106 N/C

When charging two objects by rubbing them together:

They must be made of different material

Of the following substances, which one contains the highest density of free electrons?

iron

If body M, with a positive charge, is used to charge body N by induction, what will be the nature of the charge left on the latter?

must be negative